/**
 * MIT License
 *
 * Copyright (c) 2017 Tessil
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
#ifndef TSL_ORDERED_MAP_H
#define TSL_ORDERED_MAP_H


#include <cstddef>
#include <deque>
#include <functional>
#include <initializer_list>
#include <memory>
#include <type_traits>
#include <utility>
#include <vector>
#include "ordered_hash.h"


namespace tsl {


/**
 * Implementation of an hash map using open adressing with robin hood with backshift delete to resolve collisions.
 *
 * The particularity of this hash map is that it remembers the order in which the elements were added and
 * provide a way to access the structure which stores these values through the 'values_container()' method.
 * The used container is defined by ValueTypeContainer, by default a std::deque is used (grows faster) but
 * a std::vector may be used. In this case the map provides a 'data()' method which give a direct access
 * to the memory used to store the values (which can be usefull to communicate with C API's).
 *
 * The Key and T must be copy constructible and/or move constructible. To use `unordered_erase` they both
 * must be swappable.
 *
 * The behaviour of the hash map is undefinded if the destructor of Key or T throws an exception.
 *
 * Iterators invalidation:
 *  - clear, operator=, reserve, rehash: always invalidate the iterators (also invalidate end()).
 *  - insert, emplace, emplace_hint, operator[]: when a std::vector is used as ValueTypeContainer
 *                                               and if size() < capacity(), only end().
 *                                               Otherwise all the iterators are invalidated if an insert occurs.
 *  - erase, unordered_erase: when a std::vector is used as ValueTypeContainer invalidate the iterator of
 *                            the erased element and all the ones after the erased element (including end()).
 *                            Otherwise all the iterators are invalidated if an erase occurs.
 */
template<class Key,
		 class T,
		 class Hash = std::hash<Key>,
		 class KeyEqual = std::equal_to<Key>,
		 class Allocator = std::allocator<std::pair<Key, T>>,
		 class ValueTypeContainer = std::deque<std::pair<Key, T>, Allocator>>
class ordered_map {
private:
	template<typename U>
	using has_is_transparent = tsl::detail_ordered_hash::has_is_transparent<U>;

	class KeySelect {
	public:
		using key_type = Key;

		const key_type& operator()(const std::pair<Key, T>& key_value) const noexcept {
			return key_value.first;
		}

		key_type& operator()(std::pair<Key, T>& key_value) noexcept {
			return key_value.first;
		}
	};

	class ValueSelect {
	public:
		using value_type = T;

		const value_type& operator()(const std::pair<Key, T>& key_value) const noexcept {
			return key_value.second;
		}

		value_type& operator()(std::pair<Key, T>& key_value) noexcept {
			return key_value.second;
		}
	};

	using ht = detail_ordered_hash::ordered_hash<std::pair<Key, T>, KeySelect, ValueSelect,
												 Hash, KeyEqual, Allocator, ValueTypeContainer>;

public:
	using key_type = typename ht::key_type;
	using mapped_type = T;
	using value_type = typename ht::value_type;
	using size_type = typename ht::size_type;
	using difference_type = typename ht::difference_type;
	using hasher = typename ht::hasher;
	using key_equal = typename ht::key_equal;
	using allocator_type = typename ht::allocator_type;
	using reference = typename ht::reference;
	using const_reference = typename ht::const_reference;
	using pointer = typename ht::pointer;
	using const_pointer = typename ht::const_pointer;
	using iterator = typename ht::iterator;
	using const_iterator = typename ht::const_iterator;
	using reverse_iterator = typename ht::reverse_iterator;
	using const_reverse_iterator = typename ht::const_reverse_iterator;

	using values_container_type = typename ht::values_container_type;


	/*
	 * Constructors
	 */
	ordered_map(): ordered_map(ht::DEFAULT_INIT_BUCKETS_SIZE) {
	}

	explicit ordered_map(size_type bucket_count,
						 const Hash& hash = Hash(),
						 const KeyEqual& equal = KeyEqual(),
						 const Allocator& alloc = Allocator()):
					 m_ht(bucket_count, hash, equal, alloc, ht::DEFAULT_MAX_LOAD_FACTOR)
	{
	}

	ordered_map(size_type bucket_count,
				const Allocator& alloc): ordered_map(bucket_count, Hash(), KeyEqual(), alloc)
	{
	}

	ordered_map(size_type bucket_count,
				const Hash& hash,
				const Allocator& alloc): ordered_map(bucket_count, hash, KeyEqual(), alloc)
	{
	}

	explicit ordered_map(const Allocator& alloc): ordered_map(ht::DEFAULT_INIT_BUCKETS_SIZE, alloc) {
	}

	template<class InputIt>
	ordered_map(InputIt first, InputIt last,
				size_type bucket_count = ht::DEFAULT_INIT_BUCKETS_SIZE,
				const Hash& hash = Hash(),
				const KeyEqual& equal = KeyEqual(),
				const Allocator& alloc = Allocator()): ordered_map(bucket_count, hash, equal, alloc)
	{
		insert(first, last);
	}

	template<class InputIt>
	ordered_map(InputIt first, InputIt last,
				size_type bucket_count,
				const Allocator& alloc): ordered_map(first, last, bucket_count, Hash(), KeyEqual(), alloc)
	{
	}

	template<class InputIt>
	ordered_map(InputIt first, InputIt last,
				size_type bucket_count,
				const Hash& hash,
				const Allocator& alloc): ordered_map(first, last, bucket_count, hash, KeyEqual(), alloc)
	{
	}

	ordered_map(std::initializer_list<value_type> init,
				size_type bucket_count = ht::DEFAULT_INIT_BUCKETS_SIZE,
				const Hash& hash = Hash(),
				const KeyEqual& equal = KeyEqual(),
				const Allocator& alloc = Allocator()):
			ordered_map(init.begin(), init.end(), bucket_count, hash, equal, alloc)
	{
	}

	ordered_map(std::initializer_list<value_type> init,
				size_type bucket_count,
				const Allocator& alloc):
			ordered_map(init.begin(), init.end(), bucket_count, Hash(), KeyEqual(), alloc)
	{
	}

	ordered_map(std::initializer_list<value_type> init,
				size_type bucket_count,
				const Hash& hash,
				const Allocator& alloc):
			ordered_map(init.begin(), init.end(), bucket_count, hash, KeyEqual(), alloc)
	{
	}


	ordered_map& operator=(std::initializer_list<value_type> ilist) {
		m_ht.clear();

		m_ht.reserve(ilist.size());
		m_ht.insert(ilist.begin(), ilist.end());

		return *this;
	}

	allocator_type get_allocator() const { return m_ht.get_allocator(); }



	/*
	 * Iterators
	 */
	iterator begin() noexcept { return m_ht.begin(); }
	const_iterator begin() const noexcept { return m_ht.begin(); }
	const_iterator cbegin() const noexcept { return m_ht.cbegin(); }

	iterator end() noexcept { return m_ht.end(); }
	const_iterator end() const noexcept { return m_ht.end(); }
	const_iterator cend() const noexcept { return m_ht.cend(); }

	reverse_iterator rbegin() noexcept { return m_ht.rbegin(); }
	const_reverse_iterator rbegin() const noexcept { return m_ht.rbegin(); }
	const_reverse_iterator rcbegin() const noexcept { return m_ht.rcbegin(); }

	reverse_iterator rend() noexcept { return m_ht.rend(); }
	const_reverse_iterator rend() const noexcept { return m_ht.rend(); }
	const_reverse_iterator rcend() const noexcept { return m_ht.rcend(); }


	/*
	 * Capacity
	 */
	bool empty() const noexcept { return m_ht.empty(); }
	size_type size() const noexcept { return m_ht.size(); }
	size_type max_size() const noexcept { return m_ht.max_size(); }

	/*
	 * Modifiers
	 */
	void clear() noexcept { m_ht.clear(); }



	std::pair<iterator, bool> insert(const value_type& value) { return m_ht.insert(value); }

	template<class P, typename std::enable_if<std::is_constructible<value_type, P&&>::value>::type* = nullptr>
	std::pair<iterator, bool> insert(P&& value) { return m_ht.emplace(std::forward<P>(value)); }

	std::pair<iterator, bool> insert(value_type&& value) { return m_ht.insert(std::move(value)); }


	iterator insert(const_iterator hint, const value_type& value) {
		return m_ht.insert(hint, value);
	}

	template<class P, typename std::enable_if<std::is_constructible<value_type, P&&>::value>::type* = nullptr>
	iterator insert(const_iterator hint, P&& value) {
		return m_ht.emplace_hint(hint, std::forward<P>(value));
	}

	iterator insert(const_iterator hint, value_type&& value) {
		return m_ht.insert(hint, std::move(value));
	}


	template<class InputIt>
	void insert(InputIt first, InputIt last) { m_ht.insert(first, last); }
	void insert(std::initializer_list<value_type> ilist) { m_ht.insert(ilist.begin(), ilist.end()); }




	template<class M>
	std::pair<iterator, bool> insert_or_assign(const key_type& k, M&& obj) {
		return m_ht.insert_or_assign(k, std::forward<M>(obj));
	}

	template<class M>
	std::pair<iterator, bool> insert_or_assign(key_type&& k, M&& obj) {
		return m_ht.insert_or_assign(std::move(k), std::forward<M>(obj));
	}


	template<class M>
	iterator insert_or_assign(const_iterator hint, const key_type& k, M&& obj) {
		return m_ht.insert_or_assign(hint, k, std::forward<M>(obj));
	}

	template<class M>
	iterator insert_or_assign(const_iterator hint, key_type&& k, M&& obj) {
		return m_ht.insert_or_assign(hint, std::move(k), std::forward<M>(obj));
	}

	/**
	 * Due to the way elements are stored, emplace will need to move or copy the key-value once.
	 * The method is equivalent to insert(value_type(std::forward<Args>(args)...));
	 *
	 * Mainly here for compatibility with the std::unordered_map interface.
	 */
	template<class... Args>
	std::pair<iterator, bool> emplace(Args&&... args) { return m_ht.emplace(std::forward<Args>(args)...); }

	/**
	 * Due to the way elements are stored, emplace_hint will need to move or copy the key-value once.
	 * The method is equivalent to insert(hint, value_type(std::forward<Args>(args)...));
	 *
	 * Mainly here for compatibility with the std::unordered_map interface.
	 */
	template <class... Args>
	iterator emplace_hint(const_iterator hint, Args&&... args) {
		return m_ht.emplace_hint(hint, std::forward<Args>(args)...);
	}




	template<class... Args>
	std::pair<iterator, bool> try_emplace(const key_type& k, Args&&... args) {
		return m_ht.try_emplace(k, std::forward<Args>(args)...);
	}

	template<class... Args>
	std::pair<iterator, bool> try_emplace(key_type&& k, Args&&... args) {
		return m_ht.try_emplace(std::move(k), std::forward<Args>(args)...);
	}

	template<class... Args>
	iterator try_emplace(const_iterator hint, const key_type& k, Args&&... args) {
		return m_ht.try_emplace(hint, k, std::forward<Args>(args)...);
	}

	template<class... Args>
	iterator try_emplace(const_iterator hint, key_type&& k, Args&&... args) {
		return m_ht.try_emplace(hint, std::move(k), std::forward<Args>(args)...);
	}




	/**
	 * When erasing an element, the insert order will be preserved and no holes will be present in the container
	 * returned by 'values_container()'.
	 *
	 * The method is in O(n), if the order is not important 'unordered_erase(...)' method is faster with an O(1)
	 * average complexity.
	 */
	iterator erase(iterator pos) { return m_ht.erase(pos); }

	/**
	 * @copydoc erase(iterator pos)
	 */
	iterator erase(const_iterator pos) { return m_ht.erase(pos); }

	/**
	 * @copydoc erase(iterator pos)
	 */
	iterator erase(const_iterator first, const_iterator last) { return m_ht.erase(first, last); }

	/**
	 * @copydoc erase(iterator pos)
	 */
	size_type erase(const key_type& key) { return m_ht.erase(key); }

	/**
	 * @copydoc erase(iterator pos)
	 *
	 * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
	 * as hash_function()(key). Usefull to speed-up the lookup to the value if you already have the hash.
	 */
	size_type erase(const key_type& key, std::size_t precalculated_hash) {
		return m_ht.erase(key, precalculated_hash);
	}

	/**
	 * @copydoc erase(iterator pos)
	 *
	 * This overload only participates in the overload resolution if the typedef KeyEqual::is_transparent exists.
	 * If so, K must be hashable and comparable to Key.
	 */
	template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
	size_type erase(const K& key) { return m_ht.erase(key); }

	/**
	 * @copydoc erase(const key_type& key, std::size_t precalculated_hash)
	 *
	 * This overload only participates in the overload resolution if the typedef KeyEqual::is_transparent exists.
	 * If so, K must be hashable and comparable to Key.
	 */
	template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
	size_type erase(const K& key, std::size_t precalculated_hash) {
		return m_ht.erase(key, precalculated_hash);
	}


	void swap(ordered_map& other) noexcept { other.m_ht.swap(m_ht); }

	/*
	 * Lookup
	 */
	T& at(const Key& key) { return m_ht.at(key); }

	/**
	 * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
	 * as hash_function()(key). Usefull to speed-up the lookup if you already have the hash.
	 */
	T& at(const Key& key, std::size_t precalculated_hash) { return m_ht.at(key, precalculated_hash); }


	const T& at(const Key& key) const { return m_ht.at(key); }

	/**
	 * @copydoc at(const Key& key, std::size_t precalculated_hash)
	 */
	const T& at(const Key& key, std::size_t precalculated_hash) const { return m_ht.at(key, precalculated_hash); }


	/**
	 * This overload only participates in the overload resolution if the typedef KeyEqual::is_transparent exists.
	 * If so, K must be hashable and comparable to Key.
	 */
	template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
	T& at(const K& key) { return m_ht.at(key); }

	/**
	 * @copydoc at(const K& key)
	 *
	 * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
	 * as hash_function()(key). Usefull to speed-up the lookup if you already have the hash.
	 */
	template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
	T& at(const K& key, std::size_t precalculated_hash) { return m_ht.at(key, precalculated_hash); }

	/**
	 * @copydoc at(const K& key)
	 */
	template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
	const T& at(const K& key) const { return m_ht.at(key); }

	/**
	 * @copydoc at(const K& key, std::size_t precalculated_hash)
	 */
	template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
	const T& at(const K& key, std::size_t precalculated_hash) const { return m_ht.at(key, precalculated_hash); }



	T& operator[](const Key& key) { return m_ht[key]; }
	T& operator[](Key&& key) { return m_ht[std::move(key)]; }



	size_type count(const Key& key) const { return m_ht.count(key); }

	/**
	 * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
	 * as hash_function()(key). Usefull to speed-up the lookup if you already have the hash.
	 */
	size_type count(const Key& key, std::size_t precalculated_hash) const {
		return m_ht.count(key, precalculated_hash);
	}

	/**
	 * This overload only participates in the overload resolution if the typedef KeyEqual::is_transparent exists.
	 * If so, K must be hashable and comparable to Key.
	 */
	template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
	size_type count(const K& key) const { return m_ht.count(key); }

	/**
	 * @copydoc count(const K& key) const
	 *
	 * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
	 * as hash_function()(key). Usefull to speed-up the lookup if you already have the hash.
	 */
	template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
	size_type count(const K& key, std::size_t precalculated_hash) const {
		return m_ht.count(key, precalculated_hash);
	}



	iterator find(const Key& key) { return m_ht.find(key); }

	/**
	 * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
	 * as hash_function()(key). Usefull to speed-up the lookup if you already have the hash.
	 */
	iterator find(const Key& key, std::size_t precalculated_hash) { return m_ht.find(key, precalculated_hash); }

	const_iterator find(const Key& key) const { return m_ht.find(key); }

	/**
	 * @copydoc find(const Key& key, std::size_t precalculated_hash)
	 */
	const_iterator find(const Key& key, std::size_t precalculated_hash) const {
		return m_ht.find(key, precalculated_hash);
	}

	/**
	 * This overload only participates in the overload resolution if the typedef KeyEqual::is_transparent exists.
	 * If so, K must be hashable and comparable to Key.
	 */
	template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
	iterator find(const K& key) { return m_ht.find(key); }

	/**
	 * @copydoc find(const K& key)
	 *
	 * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
	 * as hash_function()(key). Usefull to speed-up the lookup if you already have the hash.
	 */
	template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
	iterator find(const K& key, std::size_t precalculated_hash) { return m_ht.find(key, precalculated_hash); }

	/**
	 * @copydoc find(const K& key)
	 */
	template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
	const_iterator find(const K& key) const { return m_ht.find(key); }

	/**
	 * @copydoc find(const K& key)
	 *
	 * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
	 * as hash_function()(key). Usefull to speed-up the lookup if you already have the hash.
	 */
	template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
	const_iterator find(const K& key, std::size_t precalculated_hash) const {
		return m_ht.find(key, precalculated_hash);
	}



	std::pair<iterator, iterator> equal_range(const Key& key) { return m_ht.equal_range(key); }

	/**
	 * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
	 * as hash_function()(key). Usefull to speed-up the lookup if you already have the hash.
	 */
	std::pair<iterator, iterator> equal_range(const Key& key, std::size_t precalculated_hash) {
		return m_ht.equal_range(key, precalculated_hash);
	}

	std::pair<const_iterator, const_iterator> equal_range(const Key& key) const { return m_ht.equal_range(key); }

	/**
	 * @copydoc equal_range(const Key& key, std::size_t precalculated_hash)
	 */
	std::pair<const_iterator, const_iterator> equal_range(const Key& key, std::size_t precalculated_hash) const {
		return m_ht.equal_range(key, precalculated_hash);
	}

	/**
	 * This overload only participates in the overload resolution if the typedef KeyEqual::is_transparent exists.
	 * If so, K must be hashable and comparable to Key.
	 */
	template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
	std::pair<iterator, iterator> equal_range(const K& key) { return m_ht.equal_range(key); }

	/**
	 * @copydoc equal_range(const K& key)
	 *
	 * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
	 * as hash_function()(key). Usefull to speed-up the lookup if you already have the hash.
	 */
	template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
	std::pair<iterator, iterator> equal_range(const K& key, std::size_t precalculated_hash) {
		return m_ht.equal_range(key, precalculated_hash);
	}

	/**
	 * @copydoc equal_range(const K& key)
	 */
	template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
	std::pair<const_iterator, const_iterator> equal_range(const K& key) const { return m_ht.equal_range(key); }

	/**
	 * @copydoc equal_range(const K& key, std::size_t precalculated_hash)
	 */
	template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
	std::pair<const_iterator, const_iterator> equal_range(const K& key, std::size_t precalculated_hash) const {
		return m_ht.equal_range(key, precalculated_hash);
	}



	/*
	 * Bucket interface
	 */
	size_type bucket_count() const { return m_ht.bucket_count(); }
	size_type max_bucket_count() const { return m_ht.max_bucket_count(); }


	/*
	 * Hash policy
	 */
	float load_factor() const { return m_ht.load_factor(); }
	float max_load_factor() const { return m_ht.max_load_factor(); }
	void max_load_factor(float ml) { m_ht.max_load_factor(ml); }

	void rehash(size_type count) { m_ht.rehash(count); }
	void reserve(size_type count) { m_ht.reserve(count); }


	/*
	 * Observers
	 */
	hasher hash_function() const { return m_ht.hash_function(); }
	key_equal key_eq() const { return m_ht.key_eq(); }



	/*
	 * Other
	 */

	/**
	 * Convert a const_iterator to an iterator.
	 */
	iterator mutable_iterator(const_iterator pos) {
		return m_ht.mutable_iterator(pos);
	}

	/**
	 * Requires index <= size().
	 *
	 * Return an iterator to the element at index. Return end() if index == size().
	 */
	iterator nth(size_type index) { return m_ht.nth(index); }

	/**
	 * @copydoc nth(size_type index)
	 */
	const_iterator nth(size_type index) const { return m_ht.nth(index); }


	/**
	 * Return const_reference to the first element. Requires the container to not be empty.
	 */
	const_reference front() const { return m_ht.front(); }

	/**
	 * Return const_reference to the last element. Requires the container to not be empty.
	 */
	const_reference back() const { return m_ht.back(); }


	/**
	 * Only available if ValueTypeContainer is a std::vector. Same as calling 'values_container().data()'.
	 */
	template<class U = values_container_type, typename std::enable_if<tsl::detail_ordered_hash::is_vector<U>::value>::type* = nullptr>
	const typename values_container_type::value_type* data() const noexcept { return m_ht.data(); }

	/**
	 * Return the container in which the values are stored. The values are in the same order as the insertion order
	 * and are contiguous in the structure, no holes (size() == values_container().size()).
	 */
	const values_container_type& values_container() const noexcept { return m_ht.values_container(); }

	template<class U = values_container_type, typename std::enable_if<tsl::detail_ordered_hash::is_vector<U>::value>::type* = nullptr>
	size_type capacity() const noexcept { return m_ht.capacity(); }

	void shrink_to_fit() { m_ht.shrink_to_fit(); }



	/**
	 * Insert the value before pos shifting all the elements on the right of pos (including pos) one position
	 * to the right.
	 *
	 * Amortized linear time-complexity in the distance between pos and end().
	 */
	std::pair<iterator, bool> insert_at_position(const_iterator pos, const value_type& value) {
		return m_ht.insert_at_position(pos, value);
	}

	/**
	 * @copydoc insert_at_position(const_iterator pos, const value_type& value)
	 */
	std::pair<iterator, bool> insert_at_position(const_iterator pos, value_type&& value) {
		return m_ht.insert_at_position(pos, std::move(value));
	}

	/**
	 * @copydoc insert_at_position(const_iterator pos, const value_type& value)
	 *
	 * Same as insert_at_position(pos, value_type(std::forward<Args>(args)...), mainly
	 * here for coherence.
	 */
	template<class... Args>
	std::pair<iterator, bool> emplace_at_position(const_iterator pos, Args&&... args) {
		return m_ht.emplace_at_position(pos, std::forward<Args>(args)...);
	}

	/**
	 * @copydoc insert_at_position(const_iterator pos, const value_type& value)
	 */
	template<class... Args>
	std::pair<iterator, bool> try_emplace_at_position(const_iterator pos, const key_type& k, Args&&... args) {
		return m_ht.try_emplace_at_position(pos, k, std::forward<Args>(args)...);
	}

	/**
	 * @copydoc insert_at_position(const_iterator pos, const value_type& value)
	 */
	template<class... Args>
	std::pair<iterator, bool> try_emplace_at_position(const_iterator pos, key_type&& k, Args&&... args) {
		return m_ht.try_emplace_at_position(pos, std::move(k), std::forward<Args>(args)...);
	}



	void pop_back() { m_ht.pop_back(); }

	/**
	 * Faster erase operation with an O(1) average complexity but it doesn't preserve the insertion order.
	 *
	 * If an erasure occurs, the last element of the map will take the place of the erased element.
	 */
	iterator unordered_erase(iterator pos) { return m_ht.unordered_erase(pos); }

	/**
	 * @copydoc unordered_erase(iterator pos)
	 */
	iterator unordered_erase(const_iterator pos) { return m_ht.unordered_erase(pos); }

	/**
	 * @copydoc unordered_erase(iterator pos)
	 */
	size_type unordered_erase(const key_type& key) { return m_ht.unordered_erase(key); }

	/**
	 * @copydoc unordered_erase(iterator pos)
	 *
	 * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
	 * as hash_function()(key). Usefull to speed-up the lookup if you already have the hash.
	 */
	size_type unordered_erase(const key_type& key, std::size_t precalculated_hash) {
		return m_ht.unordered_erase(key, precalculated_hash);
	}

	/**
	 * @copydoc unordered_erase(iterator pos)
	 *
	 * This overload only participates in the overload resolution if the typedef KeyEqual::is_transparent exists.
	 * If so, K must be hashable and comparable to Key.
	 */
	template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
	size_type unordered_erase(const K& key) { return m_ht.unordered_erase(key); }

	/**
	 * @copydoc unordered_erase(const K& key)
	 *
	 * Use the hash value 'precalculated_hash' instead of hashing the key. The hash value should be the same
	 * as hash_function()(key). Usefull to speed-up the lookup if you already have the hash.
	 */
	template<class K, class KE = KeyEqual, typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
	size_type unordered_erase(const K& key, std::size_t precalculated_hash) {
		return m_ht.unordered_erase(key, precalculated_hash);
	}



	friend bool operator==(const ordered_map& lhs, const ordered_map& rhs) { return lhs.m_ht == rhs.m_ht; }
	friend bool operator!=(const ordered_map& lhs, const ordered_map& rhs) { return lhs.m_ht != rhs.m_ht; }
	friend bool operator<(const ordered_map& lhs, const ordered_map& rhs) { return lhs.m_ht < rhs.m_ht; }
	friend bool operator<=(const ordered_map& lhs, const ordered_map& rhs) { return lhs.m_ht <= rhs.m_ht; }
	friend bool operator>(const ordered_map& lhs, const ordered_map& rhs) { return lhs.m_ht > rhs.m_ht; }
	friend bool operator>=(const ordered_map& lhs, const ordered_map& rhs) { return lhs.m_ht >= rhs.m_ht; }

	friend void swap(ordered_map& lhs, ordered_map& rhs) { lhs.swap(rhs); }

private:
	ht m_ht;
};

} // end namespace tsl

#endif
